Substituted-(aminoxy)-pyrrolidine-2,5-dione stabilizers

ABSTRACT

Substituted-(aminoxy)-pyrrolidine-2,5-dione derivatives of the formula ##STR1## are prepared by the reaction of the appropriate maleimide and hydroxylamine compounds and are useful as stabilizers for organic polymers.

Organic polymeric materials such as plastics and resins, are subject to thermal, oxidative and photo-degradation. A great variety of stabilizers are known in the art for stabilizing a diversity of substrates. Their effectiveness varies depending upon the causes of degradation and the substrate stabilized. In general, it is difficult to predict which stabilizer will be most effective and most economical for any one area of application. For example, stabilizer effectiveness in reducing volatility may depend upon preventing bond scission in the substrate molecule. Limiting embrittlement and retaining elasticity in a polymer or rubber may require prevention of excessive crosslinking and/or chain scission. Prevention of discoloration may require inhibiting reactions which yield new chromophores or color bodies in the substrate or stabilizer. Problems of process stability and incompatibility must also be considered.

Various organic hydroxylamine compounds are generally known and some are commercially available. A number of patents disclose nitrogen-substituted hydroxylamines as antioxidant stabilizers for various substrates including polyolefins, polyesters and polyurethanes. U.S. Pat. Nos. 3,432,578, 3,644,278, 3,778,464, 3,408,422, 3,926,909, 4,316,996 and 4,386,224 are representative of such patents which basically disclose N,N-dialkyl-, N,N-diaryl and N,N-diaralkyl hydroxylamine compounds and their color improvement and color stabilizing activity.

U.S. Pat. No. 4,456,176 discloses (hydroxyphenylthio)imide stabilizers. In addition, Chemical Abstracts 93:8013 X (1980), Chemical Abstracts 86:65291r (1976), Chemical Abstracts 80:22481m (1973) and Chemical Abstracts 76:107806p (1971) disclose N-substituted derivatives of aryl succinic acid imides wherein the only substituent on the aryl group is hydroxyl. These compounds are all noted for their pharmacological activity.

It has now been determined that the (aminoxy)-pyrrolidine-2,5-dione derivatives of this invention exhibit a variety of desirable properties which makes them particularly effective and useful as stabilizers. The compounds show excellent activity in protecting polyolefins, elastomers and lubricating oils against the adverse effects of oxidative and thermal degradation. They are most effective as color improvers and process stabilizers in polyolefin compositions which may contain metal salts of fatty acids and which contain a phenolic antioxidant. Thus, they serve to substantially reduce color formation resulting from the presence of the phenolic antioxidant and/or from the processing conditions as well as to directly protect the polymer from said processing conditions. They also prevent the discoloration of polyolefin compositions containing hindered amine light stabilizers or combinations of phenolic antioxidants and organic phosphites. In addition, the gas fading that may be experienced upon exposure to the combustion products of natural gas is also significantly reduced.

It is the primary object of this invention to provide a class of pyrrolidine-2,5-dione derivatives which exhibit a broad range of improved stabilization performance characteristics.

Various other objects and advantages of this invention will become evident from the following description thereof.

The compounds of this invention correspond to the formula ##STR2## wherein

R¹ is hydrogen or alkyl of 1 to 3 carbon atoms;

R² and R³ independently are hydrogen, alkyl of 1 to 36 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 9 carbon atoms or said aralkyl substituted by alkyl of 1 to 36 carbon atoms;

X is a direct bond or phenyl;

n is 1-3;

A, when n is 1, is hydrogen, alkyl of 1 to 30 carbon atoms, aryl, cycloalkyl of 5 to 8 carbon atoms, aralkyl of 7 to 9 carbon atoms, said aralkyl substituted by alkyl of 1 to 30 carbon atoms or 2,5-dioxo-1H-pyrrole;

A, when n is 2, is alkylene of 1 to 12 carbon atoms, phenylene, cycloalkylene of 6 to 10 carbon atoms or alkylenearylenealkylene of 8 to 10 carbon atoms; and

A, when n is 3, is alkanetriyl of 3 to 6 carbon atoms or ##STR3##

R¹ is preferably hydrogen or methyl. R² and R³ are preferably straight-chain or branched alkyl of 1 to 18 carbon atoms such as methyl, ethyl, butyl, pentyl, 2-ethylhexyl, octyl, decyl, dodecyl and octadecyl; cyclopentyl and cyclohexyl; and benzyl, alpha-methylbenzyl and alpha, alpha-dimethylbenzyl. R² and R³ as benzyl is particularly preferred.

A, when n is 1, is preferably those substituents listed as preferred for R² and R³ hereinabove. Typical aryl groups include phenyl, tolyl, mesityl, xylyl and 1- and 2-naphthyl, with phenyl being preferred.

A, when n is 2, is preferably alkylene of 1 to 6 carbon atoms, including methylene, ethylene and hexylene; phenylene; cyclohexylene; and ##STR4##

The derivatives of this invention can be prepared by reacting the appropriately substituted hydroxylamine with an appropriately substituted maleimide, dimaleimide or trimaleimide in a solvent to yield the desired products. The solvent can be an aromatic hydrocarbon such as benzene, toluene, xylene, and the like, or a heterocyclic ether, such as tetrahydrofuran, optionally in the presence of an aliphatic alcohol co-solvent such as tert. butyl alcohol and the like. The reaction temperature ranges from 50° to 110° C., preferably being the reflux temperature of the system. The starting materials needed to prepare the stabilizers of this invention are items of commerce or can be prepared by known methods. For example, preparative methods for preparing cyclic imides are described in Hargreaves, Pritchard and Dave, Chemical Reviews, 70, 439-469 (1970).

The compounds of the present invention are particularly effective in stabilizing organic materials subject to oxidative, thermal and actinic degradation, such as plastics, polymers and resins.

Substrates in which these compounds are particularly useful are polyolefins such as polyethylene and polypropylene; polystyrene, including impact polystyrene, ABS resin, SBR, isoprene, as well as natural rubber, polyesters including polyethylene terephthalate and polybutylene terephthalate, including copolymers, and lubricating oils such as those derived from mineral oil.

In general polymers which can be stabilized include

1. Polymers of monoolefins and diolefins, for example polyethylene (which optionally can be crosslinked), polypropylene, polyisobutylene, polybutene-1, polymethylpentene-1, polyisoprene or polybutadiene, as well as polymers of cycloolefins, for instance of cyclopentene or norbornene.

2. Mixtures of the polymers mentioned under (1), for example mixtures of polypropylene with polyisobutylene.

3. Copolymers of monoolefins and diolefins with each other or with other vinyl monomers, such as, for example, ethylene/propylene, propylene/butene-1, propylene/isobutylene, ethylene/butene-1, propylene/butadiene, isobutylene/isoprene, ethylene/alkyl acrylates, ethylene/alkyl methacrylates, ethylene/vinyl acetate or ethylene/acrylic acid copolymers and their salts (ionomers) and terpolymers of ethylene with propylene and a diene, such as hexadiene, dicyclopentadiene or ethylidene-norbornene.

4. Polystyrene, poly-(p-methylstyrene).

5. Copolymers of styrene or methylstyrene with dienes or acrylic derivatives, such as, for example, styrene/butadiene, styrene/acrylonitrile, styrene/ethyl methacrylate, styrene/butadiene/ethyl acrylate, styrene/acrylonitrile/methyl acrylate; mixtures of high impact strength from styrene copolymers and another polymer, such as, for example, from a polyacrylate, a diene polymer or an ethylene/propylene/diene terpolymer; and block polymers of styrene, such as, for example, styrene/butadiene/styrene, styrene/isoprene/styrene, styrene/ethylene/butylene/styrene or styrene/ethylene/propylene/styrene.

6. Graft copolymers of styrene, such as, for example, styrene on polybutadiene, styrene and acrylonitrile on polybutadiene, styrene and alkyl acrylates or methacrylates on polybutadiene, styrene and acrylonitrile on ethylene/propylene/diene terpolymers, styrene and acrylonitrile on polyacrylates or polymethacrylates, styrene and acrylonitrile on acrylate/butadiene copolymers, as well as mixtures thereof with the copolymers listed under (5), for instance the copolymer mixtures known as ABS-, MBS-, ASA- or AES-polymers.

7. Halogen-containing polymers, such as polychloroprene, chlorinated rubbers, chlorinated or sulfochlorinated polyethylene, epichlorohydrine homo- and copolymers, polymers from halogen-containing vinyl compounds, as for example, polyvinylchloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, as well as copolymers thereof, as for example, vinyl chloride/vinylidene chloride, vinyl chloride/vinyl acetate or vinylidene chloride/vinyl acetate copolymers.

8. Polymers which are derived from α,β-unsaturated acids and derivatives thereof, such as polyacrylates and polymethacrylates, polyacrylamide and polyacrylonitrile.

9. Copolymers from the monomers mentioned under (8) with each other or with other unsaturated monomers, such as, for instance, acrylonitrile/butadien, acrylonitrile/alkyl acrylate, acrylonitrile/alkoxyalkyl acrylate or acrylonitrile/vinyl halogenide copolymers or acrylonitrile/alkyl methacrylate/butadiene terpolymers.

10. Polymers which are derived from unsaturated alcohols and amines, or acyl derivatives thereof or acetals thereof, such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, polyvinyl benzoate, polyvinyl maleate, polyvinylbutyral, polyallyl phthalate or polyallyl-melamine.

11. Homopolymers and copolymers of cyclic ethers, such as polyalkylene glycols, polyethylene oxide, polypropylene oxide or copolymers thereof with bis-glycidyl ethers.

12. Polyacetals, such as polyoxymethylene and those polyoxymethylenes which contain ethylene oxide as comonomer.

13. Polyphenylene oxides and sulfides, and mixtures of polyphenylene oxides with polystyrene.

14. Polyurethanes which are derived from polyethers, polyesters or polybutadiens with terminal hydroxyl groups on the one side and aliphatic or aromatic polyisocyanates on the other side, as well as precursors thereof (polyisocyanates, polyols or prepolymers).

15. Polyamides and copolyamides which are derived from diamines and dicarboxylic acids and/or from aminocarboxylic acids or the corresponding lactams, such as polyamide 4, polyamide 6, polyamide 6/6, polyamide 6/10, polyamide 11, polyamide 12, poly-2,4,4-trimethylhexamethylene terephthalamid or poly-m-phenylene isophthalamide, as well as copolymers thereof with polyethers, such as for instance with polyethylene glycol, polypropylene glycol or polytetramethylene glycols.

16. Polyureas, polyimides and polyamide-imides.

17. Polyesters which are derived from dicarboxylic acids and diols and/or from hydroxycarboxylic acids or the corresponding lactones, such as polyethylene terephthalate, polybutylene terephthalate, poly-1,4-dimethylol-cyclohexane terephthalate, poly-[2,2-(4-hydroxyphenyl)-propane] terephthalate and polyhydroxybenzoates as well as block-copolyether-esters derived from polyethers having hydroxyl end groups.

18. Polycarbonates.

19. Polysulfones, polyethersulfones and polyetherketones.

20. Crosslinked polymers which are derived from aldehydes on the one hand and phenols, ureas and melamines on the other hand, such as phenol/formaldehyde resins, urea/formaldehyde resins and melamine/formaldehyde resins.

21. Drying and non-drying alkyd resins.

22. Unsaturated polyester resins which are derived from copolyesters of saturated and unsaturated dicarboxylic acids with polyhydric alcohols and vinyl compounds as crosslinking agents, and also halogen-containing modifications thereof of low inflammability.

23. Thermosetting acrylic resins, derived from substituted acrylic esters, such as epoxy-acrylates, urethane-acrylates or polyester acrylates.

24. Alkyd resins, polyester resins or acrylate resins in admixture with melamine resins, urea resins, polyisocyanates or epoxide resins as crosslinking agents.

25. Crosslinked epoxide resins which are derived from polyepoxides, for example from bis-glycidyl ethers or from cycloaliphatic diepoxides.

26. Natural polymers, such as cellulose, rubber, gelatine and derivatives thereof which are chemically modified in a polymerhomologous manner, such as cellulose acetates, cellulose propionates and cellulose butyrates, or the cellulose ethers, such as methylcellulose.

27. Mixtures of polymers as mentioned above, for example PP/EPDM, Polyamide 6/EPDM or ABS, PVC/EVA, PVC/ABS, PVC/MBS, PC/ABS, PBTP/ABS.

28. Naturally occuring and synthetic organic materials which are pure monomeric compounds or mixtures of such compounds, for example mineral oils, animal and vegetable fats, oil and waxes, or oils, fats and waxes based on synthetic esters (e.g. phthalates, adipates, phosphates or trimellithates) and also mixtures of synthetic esters with mineral oils in ay weight ratios, which materials may be used as plasticizer for polymers or as textile spinning oils, as well as aqueous emulsions of such materials.

29. Aqueous emulsions of natural or synthetic rubber, e.g. natural latex or latices of carboxylated styrene/butadiene copolymers.

In general, the compounds of the present invention are employed in from about 0.01 to about 5% by weight of the stabilized composition, although this will vary with the particular substrate and application. An advantageous range is from about 0.5 to about 2%, and especially 0.1 to about 1%.

The stabilizers of the instant invention may readily be incorporated into the organic polymers by conventional techniques, at any convenient stage prior to the manufacture of shaped articles therefrom. For example, the stabilizer may be mixed with the polymer in dry powder form, or a suspension or emulsion of the stabilizer may be mixed with a solution, suspension, or emulsion of the polymer. The resulting stabilized polymer compositions of the invention may optionally also contain various conventional additives, such as the following.

1. Antioxidants

1.1. Alkylated monophenols, for example,

2,6-di-tert.butyl-4-methylphenol

2-tert.butyl-4,6-dimethylphenol

2,6-di-tert.butyl-4-ethylphenol

2,6-di-tert.butyl-4-n-butylphenol

2,6-di-tert.butyl-4-i-butylphenol

2,6-di-cyclopentyl-4-methylphenol

2-(α-methylcyclohexyl)-4,6-dimethylphenol

2,6-di-octadecyl-4-methylphenol

2,4,6-tri-cyclohexylphenol

2,6-di-tert.butyl-4-methoxymethylphenol

1.2. Alkylated hydroquinones, for example,

2,6-di-tert.butyl-4-methoxyphenol

2,5-di-tert.butyl-hydroquinone

2,5-di-tert.amyl-hydroquinone

2,6-diphenyl-4-octadecyloxyphenol

1.3. Hydroxylated thiodiphenyl ethers, for example

2,2'-thio-bis-(6-tert.butyl-4-methylphenol)

2,2'-thio-bis-(4-octylphenol)

4,4'-thio-bis-(6-tert.butyl-3-methylphenol)

4,4'-thio-bis-(6-tert.butyl-2-methylphenol)

1.4. Alkyliden-bisphenols, for example,

2,2'-methylene-bis-(6-tert.butyl-4-methylphenol)

2,2'-methylene-bis-(6-tert.butyl-4-ethylphenol)

2,2'-methylene-bis-[4-methyl-6-(α-methylcyclohexyl)-phenol]

2,2'-methylene-bis-(4-methyl-6-cyclohexylphenol)

2,2'-methylene-bis-(6-nonyl-4-methylphenol)

2,2'-methylene-bis-[6-(α-methylbenzyl)-4-nonylphenol]

2,2'-methylene-bis-[6-(α,α-dimethylbenzyl)-4-nonylphenol]

2,2'-methylene-bis-(4,6-di-tert.butylphenol)

2,2'-ethylidene-bis-(4,6-di-tert.butylphenol)

2,2'-ethylidene-bis-(6-tert.butyl-4-isobutylphenol)

4,4'-methylene-bis-(2,6-di-tert.butylphenol)

4,4'-methylene-bis-(6-tert.butyl-2-methylphenol)

1,1-bis-(5-tert.butyl-4-hydroxy-2-methylphenyl-butane

2,6-di-(3-tert.butyl-5-methyl-2-hydroxybenzyl)-4-methylphenol

1,1,3-tris-(5-tert.butyl-4-hydroxy-2-methylphenyl)-butane

1,1-bis-(5-tert.butyl-4-hydroxy-2-methylphenyl)-3-n-dodecylmercaptobutane

ethylenglycol-bis-[3,3-bis-(3'-tert.butyl-4'-hydroxyphenyl)-butyrat]

di-(3-tert.butyl-4-hydroxy-5-methylphenyl)-dicyclopentadien

di-[2-(3'-tert.butyl-2'-hydroxy-5'-methyl-benzyl)-6-tert.butyl-4-methylphenyl]-terephthalate.

1.5. Benzyl compounds, for example,

1,3,5-tri-(3,5-di-tert.butyl-4-hydroxybenzyl)-2,4,6-trimethylbenzene-di-(3,5-di-tert.butyl-4-hydroxybenzyl)sulfide

3,5-di-tert.butyl-4-hydroxybenzyl-mercapto-acetic acid isooctyl ester

bis-(4-tert.butyl-3-hydroxy-2,6-dimethylbenzyl)dithiolterephthalate

1,3,5-tris-(3,5-di-tert.butyl-4-hydroxybenzyl)-isocyanurate

1,3,5-tris-(4-tert.butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanurate

3,5-di-tert.butyl-4-hydroxybenzyl-phosphoric acid-dioctadecyl ester

3,5-di-tert.butyl-4-hydroxybenzyl-phosphoric acid-monoethyl ester, calcium-salt

1.6. Acylaminophenols, for example,

4-hydroxy-lauric acid anilide

4-hydroxy-stearic acid anilide

2,4-bis-octylmercapto-6-(3,5-tert.butyl-4-hydroxyanilino)-s-triazine

octyl-N-(3,5-di-tert.butyl-4-hydroxyphenyl)-carbaminate

1.7. Esters of β-(3,5-di-tert.butyl-4-hydroxyphenyl)-propionic acid with monohydric or polyhydric alcohols, for example,

    ______________________________________                                         methanol        diethyleneglycol                                               octadecanol     triethyleneglycol                                              1,6-hexanediol  pentaerythritol                                                neopentylglycol tris-hydroxyethyl isocyanurate                                 thiodiethyleneglycol                                                                           di-hydroxyethyl oxalic acid                                                    diamide                                                        ______________________________________                                    

1.8. Ester of β-(5-tert.butyl-4-hydroxy-3-methylphenyl)-propionic acid with monohydric or polyhydric alcohols, for example,

    ______________________________________                                         methanol        diethyleneglycol                                               octadecanol     triethyleneglycol                                              1,6-hexanediol  pentaerytritol                                                 neopentylglycol tris-hydroxyethyl isocyanorate                                 thiodiethyleneglycol                                                                           di-hydroxyethyl oxalic acid                                                    diamide                                                        ______________________________________                                    

1.9. Amides of β-(3,5-di-tert.butyl-4-hydroxyphenyl)propionic acid for example,

N,N'-di-(3,5-di-tert.butyl-4-hydroxyphenylpropionyl)hexamethylendiamine

N,N'-di-(3,5-di-tert.butyl-4-hydroxyphenylpropionyl)trimethylendiamine

N,N'-di-(3,5-di-tert.butyl-4-hydroxyphenylpropionyl)hydrazine

2. UV absorbers and light stabilisers

2.1. 2-(2'-Hydroxyphenyl)-benztriazoles, for example, the 5'-methyl-, 3',5'-di-tert.butyl-, 5'-tert.butyl-, 5'-(1,1,3,3-tetramethylbutyl)-, 5-chloro-3',5'-di-tert.butyl-, 5-chloro-3'-tert.butyl-5'-methyl-, 3'-sec.butyl-5'-tert.butyl-, 4'-octoxy, 3',5'-di-tert.amyl-, 3',5'-bis-(α,α-dimethylbenzyl)-derivative.

2.2. 2-Hydroxy-benzophenones, for example, the 4-hydroxy-, 4-methoxy-, 4-octoxy, 4-decyloxy-, 4-dodecyloxy-, 4-benzyloxy, 4,2',4'-trihydroxy- and 2'-hydroxy-4,4'-dimethoxy derivative.

2.3. Ester of optionally substituted benzoic acids for example, phenyl salicylate, 4-tert.butyl-phenylsalicilate, octylphenyl salicylate, dibenzoylresorcinol, bis-(4-tert.butylbenzoyl)-resorcinol, benzoylresorcinol, 3,5-di-tert.butyl-4-hydroxybenzoic acid 2,4-di-tert.butyl-phenyl ester and 3,5-di-tert.-butyl-4-hydroxybenzoic acid hexadecyl ester.

2.4. Acrylates, for example, -cyano-β,β-diphenylacrylic acid ethyl ester or isooctyl ester, -carbomethoxy-cinnamic acid methyl ester, -cyano-β-methyl-p-methoxy-cinnamic acid methyl ester or butyl ester, -carbomethoxy-p-methoxy-cinnamic acid methyl ester, N-(β-carbomethoxy-β-cyanovinyl)-2-methyl-indoline.

2.5 Nickel compounds, for example, nickel complexes of 2,2'-thio-bis-[4-(1,1,3,3-tetramethylbutyl)-phenol], such as the 1:1 or 1:2 complex, optionally with additional ligands such as n-butylamine, triethanolamine or N-cyclohexyl-di-ethanolamine, nickel dibutyldithiocarbamate, nickel salts of 4-hydroxy-3,5-di-tert.butylbenzylphosphonic acid monoalkyl esters, such as of the methyl, ethyl or butyl ester, nickel complexes of ketoximes such as of 2-hydroxy-4-methyl-phenyl undecyl ketoxime, nickel complexes of 1-phenyl-4-lauroyl-5-hydroxy-pyrazol, optionally with additional ligands.

2.6. Sterically hindered amines, for example bis-(2,2,6,6-tetramethylpiperidyl)-sebacate bis-(1,2,2,6,6-pentamethylpiperidyl)-sebacate n-butyl-3,5-di-tert.butyl-4-hydroxybenzyl malonic acid bis-(1,2,2,6,6-pentamethylpiperidyl)ester, condensation product of 1-hydroxyethyl-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid, condensation product of N,N'-(2,2,6,6-tetramethylpiperidyl)-hexamethylendiamine and 4-tert.octylamino-2,6-dichloro-1,3,5-s-triazine, tris-(2,2,6,6-tetramethylpiperidyl)-nitrilotriacetate, tetrakis-(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane-tetracarbonic acid, 1,1'(1,2-ethanediyl)-bis-(3,3,5,5-tetramethylpiperazinone).

2.7. Oxalic acid diamides, for example, 4,4'-di-octyloxy-oxanilide, 2,2'-di-octyloxy-5,5'-di-tert.butyl-oxanilide, 2,2'-di-dodecyloxy-5,5'-di-tert.butyl-oxanilide, 2-ethoxy-2'-ethyl-oxanilide, N,N'-bis (3-dimethylaminopropyl)-oxalamide, 2-ethoxy-5-tert.butyl-2'-ethyloxanilide and its mixture with 2-ethoxy-2'-ethyl-5,4'-di-tert.butyloxanilide and mixtures of ortho- and para-methoxy-as well as of o- and p-ethoxy-disubstituted oxanilides.

3. Metal deactivators, for example, N,N'-diphenyloxalic acid diamide, N-salicylal-N'-salicyloylhydrazine, N,N'-bis-salicyloylhydrazine, N,N'-bis-(3,5-di-tert.butyl-4-hydroxyphenylpropionyl)-hydrazine, 3-salicyloylamino-1,2,4-triazole, bis-benzyliden-oxalic acid dihydrazide.

4. Phosphites and phosphonites, for example, triphenyl phosphite, diphenylalkyl phosphites, phenyldialkyl phosphites, tri-(nonylphenyl)phosphite, trilauryl phosphite, trioctadecyl phosphite, di-stearyl-pentaerythrit diphosphite, tris-(2,4-di-tert.butylphenyl) phosphite, di-isodecylpentaerythritol diphosphite, di-(2,4-di-tert.butylphenyl)pentaerythritol diphosphite, tristearyl-sorbite triphosphite, tetrakis-(2,4-di-tert.butylphenyl)-4,4'-diphenylylendiphosphonite.

5. Compounds which destroy peroxide, for example, esters of β-thiodipropionic acid, for example the lauryl, stearyl, myristyl or tridecyl esters, mercapto-benzimidazole or the zinc salt of 2-mercaptobenzimidazole, zinc-dibutyl-dithio-carbamate, dioctadecyldisulfide, pentaerythritol-tetrakis-(β-dodecylmercapto)-propionate.

6. Polyamide stabilisers, for example copper salts in combination with iodides and/or phosphorus compounds and salts of divalent manganese.

7. Basic co-stabilisers, for example, melamine, polyvinyl-pyrrolidone, dicyandiamide, triallyl cyanurate, urea derivatives, hydrazine derivatives, amines, polyamides, polyurethanes, alkali metal salts and alkaline earth metal salts of higher fatty acids for example Ca stearate, Zn stearate, Mg stearate, Na ricinoleate and K palmitate, antimony pyrocatecholate or zinc pyrocatecholate.

8. Nucleating agents, for example, 4-tert.butyl-benzoic acid, adipic acid, diphenylacetic acid.

9. Fillers and reinforcing agents, for example, calcium carbonate, silicates, glass fibres, asbestos, talc, kaolin, mica, barium sulfate, metal oxides and hydroxides, carbon black, graphite.

10. Other additives, for example, plasticizers, lubricants, emulsifiers, pigments, optical brighteners, flameproofing agents, anti-static agents, blowing agents and thio-synergists such as dilaurylthiodipropionate or distearyl-thiodipropionate.

While the instant derivatives can be beneficially used as stabilizers for a variety of substrates, particularly the polyolefins, both alone and in conjunction with other coadditives, the introduction of the instant derivatives into polyolefins, optionally containing various alkali metal, alkaline earth metal and aluminum salts of higher fatty acids (see Additive #7 hereinabove), with hindered phenolic antioxidants provides enhanced and particularly salubrious protection to such substrates in terms of reducing color formation stemming from the presence of the phenols. Such phenolic antioxidants include n-octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, neopentanetetrayl tetrakis-(3,5-di-tert-butyl-4-hydroxyl-hydrocinnamate), di-n-octadecyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, thiodiethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 3,6-di-oxaoctamethylene bis(3-methyl-5-tert-butyl-4-hydroxyhydrocinnamate), 2,6-di-tert-butyl-p-cresol, 2,2'-ethylidene-bis(4,6-di-tert-butylphenol), 1,3,5-tris(2,6-di-methyl-4-tert-butyl-3-hydroxybenzyl)isocyanurate, 1,1,3-tris-(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,3,5-tris-[2-(3,5-di-tert-butyl-4-hydroxyhydro-cinnamoyloxy)-ethyl]-isocyanurate, 3,5-di-(3,5-di-tert-butyl-4-hydroxybenzyl)-mesitol, hexamethylene bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 1-(3,5-di-tert-butyl-4-hydroxyanilino)-3,5-di(octylthio)-s-triazine, N,N'-hexamethylene-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamamide), calcium bis(ethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate), ethylene bis[3,3-di(3-tert-butyl-4-hydroxyphenyl)butyrate], octyl 3,5-di-tert-butyl-4-hydroxybenzylmercaptoacetate, bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazide, and N,N'-bis[2-(3,5-tert-butyl-4-hydroxyhydroxo-cinnamoyloxy)ethyl]-oxamide, and preferably neopentanetetrayl tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), n-octadecyl 3,5-di-tert-butyl-4hydroxyhydrocinnamate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 2,6-di-tert-butyl-p-cresol or 2,2'-ethylidene-bis(4,6-di-tert-butylphenol).

Likewise, the instant compounds prevent color formation when hindered amine light stabilizers are present, such hindered amines including bis(1,2,2,6,6,-pentamethyl-4-piperidyl)-2-n-butyl-2-(3,5-di-tert-butyl-4-hydroxy-benzyl) malonate; bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate; dimethylsuccinate polymer with 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol; and polymer of 2,4-dichloro-6-octylamino-s-triazine with N'-(2,2,6,6-tetramethyl-4-piperidyl)hexamethylene diamine.

The following examples illustrate the embodiments of this invention. In these examples, all parts given are by weight unless otherwise specified.

EXAMPLE 1 N-Phenyl-3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione

A suspension of 6.0 g (28 mmole) of N,N-dibenzylhydroxylamine and 4.87 g (28 mmole) of N-phenylmaleimide in 50 ml of dry tetrahydrofuran is heated at reflux for 40 hours. The solvent is removed in vacuo and the residue is recrystallized from toluene to give 6.1 g (56%) of a white solid, mp 91°-93° C.:

Anal. Calcd. for C₂₄ H₂₂ N₂ O₃ : C, 74.6; H, 5.7; N, 7.3. Found: C, 74.6; H, 5.6; N, 7.2.

EXAMPLE 2 N-n-Octadecyl-3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione

The procedure of Example 1 is repeated using 6.10 g (29 mmole) of N,N-dibenzylhydroxylamine and 10.0 g (29 mmole) of N-n-octadecylmaleimide. The residue is purified by preparative HPLC (Silica gel: 9:1 heptane:ethyl acetate eluent) to give 8.0 g (49%) of a waxy solid.

Anal. Calcd. for C₃₆ H₅₄ N₂ O₃ : C, 76.8; H, 9.7; N, 5.0. Found: C, 76.8; H, 9.6; N, 4.8.

EXAMPLE 1,2-Bis[3-[(N,N-dibenzylamino)oxy]-2,5-dioxopyrrolidin-1-yl]benzene

The procedure of Example 1 is repeated using 5.33 g (25 mmole) of N,N-dibenzylhydroxylamine and 3.35 g (12.5 mmole) of N,N'-ortho-phenylenedimaleimide. The residue is purified by preparative HPLC (Silica gel: 7:3 heptane:ethyl acetate eluent) to give 5.9 g (34%) of a white solid.

Anal. Calcd. for C₄₂ H₃₈ N₄ O₆ : C, 72.6; H, 5.5; N, 8.1. Found: C, 72.6 H, 5.4; N, 7.9.

EXAMPLE 4 1-[3-[(N,N-Dibenzylamino)oxy]2,5-dioxopyrrolidin-1-yl]-2-(2,5-dioxo-1H-pyrrole-1-yl)benzene

From the residue of Example 3, 0.6 g of the mono-adduct is isolated by preparative HPLC as a white solid.

Anal. Calcd. for C₂₈ H₂₃ N₃ O₅ : C, 69.8; H, 4.8; N, 8.3. Found: C, 70.0; H, 5.1; N, 8.5.

EXAMPLE 5 N-Cyclohexyl-3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione

The procedure of Example 1 is repeated using 5.33 g (25 mmole) of N,N-dibenzylhydroxylamine and 4.48 g (25 mmole) of N-cyclohexylmaleimide. The residue was crystallized from ethanol to give 6.0 g (61%) of a white solid, mp 75°-77° C.

Anal. Calcd. for C₂₄ H₂₈ N₂ O₃ ; C, 73.4; H, 7.2; N, 7.1. Found: C, 73.8; H, 7.1; N, 7.1.

EXAMPLE 6 1,1-Bis[4-[3-((N,N-dibenzylamino)oxy)pyrrolidine-2,5-dione-1-yl]-phenyl]methane

The procedure of Example 1 is repeated using 5.33 g (25 mmole) of N,N-dibenzylhydroxylamine and 4.48 g (12.5 mmole) of 1,1-(methylenedi-4,1-phenylene)bismaleimide.

The residue is purified by preparative HPLC (Silica gel: 7:3 heptane:ethyl acetate eluent), to give 6.0 g (61%) of white solid, m.p. 141°-149° C. V

Anal. Calcd. for C₄₉ H₄₄ N₄ O₆ : C, 75.0; H, 5.6; N, 7.1. Found: C, 75.1; H, 5.8; N, 7.0.

EXAMPLE 7 N-Phenyl-3-[(N,N-diethylamino)oxy]pyrrolidine-2,5-dione

The procedure of Example 1 is repeated using 4.46 g (50 mmole) of N,N-diethylhydroxylamine and 8.66 g (50 mmole) of N-phenylmaleimide.

The residue is recrystallized from ethanol to give 6.1 g. (46%) of an off-white solid, m.p. 110°-112° C.

Anal. Calcd. for C₁₄ H₁₈ N₂ O₃ : C, 64.1; H, 6.9; N, 10.7. Found: C, 63.9; H, 6.8; N, 10.5.

EXAMPLE 8 N-methyl-3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione

The procedure for Example 1 is repeated using 5.33 g (25 mmole) of N,N-dibenzylhydroxylamine and 2.78 g (25 mmole) of N-methylmaleimide.

The residue is purified by preparative HPLC (Silica gel: 4:1 heptane:ethyl acetate eluent) to give 7.6 g (94%) of a clear liquid.

Anal. Calcd. for C₁₉ H₂₀ N₂ O₃ : C, 70.4; H, 6.2; N, 8.6. Found: C, 70.2; H, 6.3; N, 8.6.

EXAMPLE 9 3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione

The procedure of Example 1 is repeated using 5.33 g (25 mmole) of N,N-dibenzylhydroxylamine and 2.42 g (25 mmole) of maleimide. The residue is purified by preparative HPLC (Silica gel: 4:1 heptane:ethyl acetate eluent) to give 5.4 g (74%) of a colorless gum.

Anal. Calcd. for C₁₈ H₁₈ N₂ O₃ : C, 69.7; H, 5.8; N, 9.0. Found: C, 69.9; H, 5.8; N, 9.0.

EXAMPLE 10 1,6-Di{3-[(N,N-dibenzylamino)oxy)-2,5-dioxopyrrolidin-1-yl}hexane

The procedure of Example 1 is repeated using 3.08 g (14.5 mmole) of N,N-dibenzylhydroxylamine and 2.0 g (7.2 mmole) of 1,6-hexanediyl bis(maleimide).

EXAMPLE 11 Processing of Polypropylene Base Formulation

    ______________________________________                                         Polypropylene*  100          parts                                             Calcium Stearate                                                                               0.10         part                                              ______________________________________                                          *Profax 6501 from Himont U.S.A.                                          

Stabilizers are solvent blended into polypropylene as solutions in methylene chloride and after removal of solvent by evaporation at reduced pressure, the resin is extruded using the following extruder conditions:

    ______________________________________                                                     Temperature (°C.)                                           ______________________________________                                         Cylinder #1   232                                                              Cylinder #2   246                                                              Cylinder #3   260                                                              Gate #1       260                                                              Gate #2       260                                                              Gate #3       260                                                              RPM 100                                                                        ______________________________________                                    

During extrusion, the internal extruder pressure is determined using a pressure transducer. After each of the first, third and fifth extrusions, resin pellets are compression molded into 125. mil (3.2 mm) thick plaques at 193° C. and specimen yellowness index (Y.I.) determined according to ASTM D1925-63T.

The melt flow rate (MFR) is determined by ASTM method 1238 condition L. The melt flow rate varies inversely as the transducer pressure and both are a measure of the molecular weight for a specific type of polymer. The results are shown in the following tables.

    ______________________________________                                                                 MFR                                                                YI Color    After Extrusion                                                    After Extrusion                                                                            (g/10 min)                                             Additives     1      3       5    1      5                                     ______________________________________                                         Base Resin    3.6    3.9     4.6  4.4    11.5                                  0.1% Antioxidant A*                                                                          6.1    7.9     9.4  2.5    4.2                                   0.1% Antioxidant A +                                                                         4.2    4.9     5.3  2.1    3.2                                   0.05% Ex. 1                                                                    0.1% Antioxidant A +                                                                         3.0    4.1     6.2  2.0    3.4                                   0.05% Ex. 2                                                                    0.1% Antioxidant A +                                                                         3.8    6.8     6.1  2.0    3.1                                   0.05% Ex. 3                                                                    Base Resin    3.8    4.0     4.4                                               0.1% Antioxidant A                                                                           10.9   12.0    14.4                                              0.1% Antioxidant A +                                                                         7.7    9.1     11.0                                              0.05% Ex. 6                                                                    0.1% Antioxidant A +                                                                         7.2    8.9     9.6                                               0.05% Ex. 7                                                                    ______________________________________                                          *Neopentyl tetrakis[3(3',5di-tert. butyl4hydroxy-phenyl)propanoate       

These data thus illustrate the effective stabilization activity and excellent performance characteristics of the instant compounds.

Summarizing, it is seen that this invention provides novel substituted (aminoxy)-pyrrolidine-2,5-dione stabilizers and color improvers. Variations may be made in proportions, procedures and materials without departing from the scope of the instant invention as defined by the following claims. 

What is claimed is:
 1. A compound of the formula ##STR5## wherein R¹ is hydrogen or alkyl of 1 to 3 carbon atoms;R² and R³ independently are hydrogen, alkyl of 1 to 36 carbon atoms, cycloalkyl of 5 to 12 carbon atoms, aralkyl of 7 to 9 carbon atoms or said aralkyl substituted by alkyl of 1 to 36 carbon atoms; X is a direct bond or phenyl; n is 1-3; A, when n is 1, is hydrogen, alkyl of 1 to 30 carbon atoms, aryl, cycloalkyl of 5 to 8 carbon atoms, aralkyl of 7 to 9 carbon atoms, said aralkyl substituted by alkyl of 1 to 30 carbon atoms or 2,5-dioxo-1 H-pyrrole; A, when n is 2, is alkylene of 1 to 12 carbon atoms, phenylene, cycloalkylene of 6 to 10 carbon atoms or alkylenearylenealkylene of 8 to 10 carbon atoms; and A, when n is 3, is alkanetriyl of 3 to 6 carbon atoms or ##STR6##
 2. The compound of claim 1, wherein R¹ is hydrogen or methyl; and R² and R³ independently are alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 6 carbon atoms; or benzyl, α-methylbenzyl or α,α-dimethylbenzyl.
 3. The compound of claim 2, wherein R² and R³ are both benzyl.
 4. The compound of claim 1, wherein n is
 1. 5. The compound of claim 4, wherein A is alkyl of 1 to 18 carbon atoms, cycloalkyl of 5 to 6 carbon atoms, benzyl, α-methylbenzyl, α,α-dimethylbenzyl or phenyl.
 6. The compound of claim 1, wherein n is
 2. 7. The compound of claim 6, wherein A is alkylene of 1 to 6 carbon atoms, phenylene, cyclohexylene or ##STR7##
 8. N-Phenyl-3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione according to claim
 5. 9. N-n-Octadecyl-3-[(N,N-dibenzylamino)oxy]pyrolidine-2,5-dione according to claim
 5. 10. 1,2-Bis[3-[(N,N-dibenzylamino)oxy]-2,5-dioxopyrrolidin-1-yl]benzene according to claim
 7. 11. 1-[3-[(N,N-Dibenzylamino)oxy]2,5-dioxo-pyrrolidin-1-yl]-2-(2,5-dioxo-1H-pyrrole-1-yl)benzene according to claim
 1. 12. N-Cyclohexyl-3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione according to claim
 5. 13. 1,1-Bis[4-[3-((N,N-dibenzylamino)oxy) pyrrolidine-2,5-dione-1-yl]-phenyl]methane according to claim
 7. 14. N-Phenyl-3-[(N,N-diethylamino)oxy]pyrrolidine-2,5-dione according to claim
 5. 15. N-methyl-3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione according to claim
 5. 16. 3-[(N,N-dibenzylamino)oxy]pyrrolidine-2,5-dione according to claim
 5. 17. 1,6-Di{3-[(N,N-dibenzylamino)oxy]-2,5-dioxopyrrolidin-1-yl}hexane according to claim
 7. 18. A composition of matter comprising an organic material subject to oxidative, thermal and actinic degradation stabilized with an effective stabilizing amount of a compound of claim
 1. 19. The composition of claim 18, wherein the organic material is a synthetic polymer.
 20. The composition of claim 19, wherein said synthetic polymer is a polyolefin homopolymer or copolymer.
 21. The composition of claim 20 which also contains a metal salt of a higher fatty acid.
 22. The composition of claim 18 which also contains a phenolic antioxidant.
 23. The composition of claim 21 which also contains a phenolic antioxidant.
 24. The composition of claim 22, whrein said phenolic antioxidant is selected from the group consisting of neopentanetetrayl tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), n-octadecyl 3,5-di-tert-butyl-4-hydroxyhydrocinnamate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, 1,3,5-tris-(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate, 2,6-di-tert-butyl-p-cresol or 2,2'-ethylidene-bis(4,6-di-tert-butylphenol).
 25. A method for stabilizing an organic material against oxidative, thermal and actinic degradation which comprises incorporating into said organic material an effective stabilizing amount of a compound of claim
 1. 